Effects of increased stroke number on sequential arm movements in Parkinson's disease subjects.

To examine whether multiple-component movements performed by Parkinson's disease (PD) patients are impaired differentially depending on the number of strokes, 10 PD patients and 10 age-matched control subjects performed sequential arm movements with one, two or three strokes on a digitizer. The patients were slower than the controls in executing the movement sequences and showed prolonged delays between strokes. These slowing characteristics were accentuated as stroke number increased from two to three. These results suggest that PD patients have a reduced capacity to process information rapidly, thereby limiting their ability to perform complex movements.